pstore: change mutex locking to spin_locks
pstore was using mutex locking to protect read/write access to the
backend plug-ins. This causes problems when pstore is executed in
an NMI context through panic() -> kmsg_dump().
This patch changes the mutex to a spin_lock_irqsave then also checks to
see if we are in an NMI context. If we are in an NMI and can't get the
lock, just print a message stating that and blow by the locking.
All this is probably a hack around the bigger locking problem but it
solves my current situation of trying to sleep in an NMI context.
Tested by loading the lkdtm module and executing a HARDLOCKUP which
will cause the machine to panic inside the nmi handler.
Signed-off-by: Don Zickus <dzickus@redhat.com>
Acked-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
diff --git a/include/linux/pstore.h b/include/linux/pstore.h
index cc03bbf..b91440e 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -32,7 +32,7 @@
struct pstore_info {
struct module *owner;
char *name;
- struct mutex buf_mutex; /* serialize access to 'buf' */
+ spinlock_t buf_lock; /* serialize access to 'buf' */
char *buf;
size_t bufsize;
int (*open)(struct pstore_info *psi);